When a whole word must cross between clocks at a low rate, a handshake is the signoff-safe answer: control travels as synchronised levels and the data bus crosses without a synchroniser because the protocol holds it stable. For the design-side construction see the CDC handshakes RTL lessons; here the emphasis is on why each variant is safe, what it costs, and what valid/ready needs around it to qualify.
Lesson | After it you can... |
|---|---|
Walk through the four steps and say why levels make it safe. | |
Trade latency and throughput against the four-phase variant. | |
Explain why plain valid/ready is not CDC-safe and what to wrap it in. | |
Compute round-trip cost symbolically in source and destination cycles. |
Suggested order: read the four lessons in page order; pulse-scheme readers should start from Pulse Synchronizers first.
The data is held stable from before the request rises until after the acknowledge returns, so the destination always samples a settled bus. Only the single-bit control signals change asynchronously and need synchronisers.